The present invention is directed to improved apparatus for measuring the magnetic properties of magnetic amplifier cores.
Progress in the development of better magnetic materials led to the design of magnetic amplifier systems and other types of switching reactors and transformers. Since the origin of the magnetic amplifier (circa 1950), and the concurrent growth of semiconductor technology, magnetic circuits of various types have been employed in a very large assortment of electronic systems. The principal contribution of these circuits has been smaller size, lower cost, and a great improvement in efficiency, due in a large part to improved magnetic core materials.
The current wide usage of these core materials has warranted a close look at the test equipment being used for evaluation of the cores.
Basically a prior art test set for measuring magnetic properties of magnetic amplifier cores includes a device for receiving a magnetic amplifier core for test. This device includes a primary winding for providing a drive signal to produce a magnetic field in the test core and a secondary winding for sensing an output signal indicative of the magnetic flux produced in the core in response to the drive signal. However, no provision is made for direct reading of magnetic properties on calibrated scales, which means that each measurement taken must be followed by mathematical calculations to arrive at the correct interpretation.
A typical prior art test set also necessarily includes an electrical circuit for producing a repetitive constant current drive signal having a variable voltage, such as a sinusoidal waveform signal. The electrical circuit for producing the drive signal which is provided by the primary winding typically includes magnetic components such as transformers for providing the peak power levels at which the magnetic cores must be tested. Because it takes several hours on the part of a skilled engineer to test one core, the magnetic amplifier core is almost the only component part placed in stock with no inspection tests. To inspect every core, even in a small lot of 50 cores or less, would be untenable, and therefore is not done. In effect, the prior art test sets have been found to be commercially impractical for use in testing magnetic amplifier cores. Accordingly, most users of the cores rely solely on the performance characteristics as published in core supplier catalogs. In many cases, the user of the core designs it into a circuit expected to perform in a manner not covered by the published characteristics. As a result of the very cumbersome and inadequate test methods used by the core supplier, and the lack of practical equipment to measure the cores during the design phase of the end item equipment, the design of magnetic circuits is more an "art" than a science.
In addition (and perhaps more serious) due to lack of practical test equipment, magnetic amplifier cores that are received in large quantities often are placed in stock for use in production without benefit of any kind of receiving inspection tests. This situation leads to increased manufacturing costs due to scrap and rework, and in many cases marginal or defective equipment is allowed to reach the field.